Decolorization of acrylic and alpha-alkylacrylic acids and their derivatives



mama Feb. '12, 1940 DECOLOBIZATION OF ACRYLIC AND a- ALKYLACRYLIC ACIDS AND THEIR DE- RIVATIVES William P. Utermohlen, Jr., Kingsport, Tenn, aa-

signor to Eastman Kodak Company, Rochester. N. Y., a corporation of New Jersey No Drawing. Application January 7, 1M3,

Serial No. 471,607 5 6 Claims.

This invention relates to the decolorization of acrylic and a-allwlacrylic acids and their deriw atives. I

In the preparation of acrylic and e-alkylacrylic acids by oxidation of acrolein and a-alkyl acroleins, an undesirable color frequently develops in the acids, owing to the fact that phenolic polymerization inhibitors, e. g. hydroquinone, have been used to preserve acrolein or e-alkyl acro= lein. Moreover, acrylic acid and a-alkylacryllc acids which have beenstored containing a plienolic polymerization inhibitor frequently develop undesirable color. This color persists even in monomeric compounds, e. e. esters, prepared from the colored acids. The color aho persists in polymerization products prepared from the colored acids or their derivatives. The color is caused by oxidation products of the phenolic polymerization inhibitors, 1 have found.

It is, accordingly, an object of my invention to provide a process for decolorizlng the aforesaid colored acids and monomeric products prepared from the acids. Uther objects will become apparent hereinafter.

accordance with the invention, I decolorire colored monomeric compounds selected from the group consisting of acrylic acid, a-allrylacrylic acids and monomeric compounds prepared from the colored acrylic acid and a-alkylacryllc acids,

such as esters of these acids, the color oi said colored monomeric compounds being caused. by the presence oi colored oxidation products of phenolic polymerization inhibitors, by treating the colored monomeric compounds with an alkali metal bisulilte. The monomeric acids are ad vantageously dissolved in a water immiscible solvent and the resulting solution washed with an aqueous solution of an alkali metal bisuliite to effect the decolorization. As suitable water immiscible solvents, dlethyl ether, a mixture or iiiethyl ether and methylene chloride, and benzene are exemplary. With water immiscible derivatives oi the colored acids, the derivatives can allvantageously be treated directly with an aqueous solution 02 the alkali metal bisulfite.

- The following examples will serve to illustrate the manner of practicing my invention:

Example 1 a-ldethacrylic acid which had been prepared by the oxidation of a-methacrolein which contained hydroquinone as a polymerization inhibitor turned to a deep wine c0101 upon prolonged standing. This colored material was diluted with diethyl ether and the ethereal solution was washed with a small quantity off a 20 percent aqueous solution or sodium blsulflte. The resultingethereal solution became practically colorless. The colorless ethereal solution was dried over anhydrous sodium sullite, the ether removed and the colorless s-methacrylic acid recovered by distillation in vacuo in a colorless form.

Example 2 sodium sulfate, the benreneremoved' and the e ethacryllc acid recovered by distillation in vacuo. Resinous polymers prepared from this color-dies wethacrylic acid remained colorless.

Example 3 llsobutyl a-ethacrylate, prepared by esterification of m-ethacryllc acid with isobutyl alcohol (see the copenolina application oi R. L. Hasche and P. Utermohlen, Jzn, Serial No. 471,608, filed or even date herewith) which was yellow due to the presence of oxidation products of hydroquinone which have been employed in the a-ethacrylic acid, was washed with a cold. dilute solution or potassium carbonate and then with water. The washed. product was dried over anhydrous sodium sulfate and distilled in vacuo in an all class still; A light yellow color persisted in the distillate and a second distillation in vacuo did not remove the color. The otherwise pure ester was then washed with a 20 wrcent aqueour. solution oi sodium'bisulflte. The washed esmr was then lurther washed with a dilute potassium carbonate solution and finally with water. The washed ester was then dried over anhydrous sodlum suliate and then distilled in vacuo. The resulting product was water-white and developed no color upon. standing or upon being subjected to polymerization conditions.

In a similar manner, other colored acrylic and a-alkylacryllc acids and their colored derivatives can be efleotively decolorized when the undesirable coloration results from the oxidation 01' phenolic polymerization inhibitors.

whatlclaimasmyinventionanddesireto be secured by Letters Patent of the United States is:

1. A process for decolor a colored monomeric acid selected, from the group consisting of acrylic acid and a-alkacrylic acids in which the alkyl group contains from 1 to 2 carbon atoms, the color of said monomeric acid being caused by the presence of colored oxidation products of phenolic polymerization inhibitors, comprising treating a solution of the colored acid in a water immiscible organic solvent with an aqueous solution of an alkali metal bisulflte.

2. A process for decolorizing a colored monomeric acid selected from the group consisting of acrylic acid and a-alkacrylic acids in which the alkyl group contains from 1 to 2 carbon atoms, the color of said monomeric acid being caused by the presence of colored oxidation products of phenolic polymerization inhibitors, comprising treating a solution of the colored acid in a water immiscible organic solvent with an aqueous solution of sodium'bisulflte.

3. A process for decolorizing monomeric a-methacrylic acid, the color of the a-methacrylic acid being caused by the presence of colored oxidation products of phenolic polymerization inhibitors, comprising treatinga solution of, the colored s-methacrylic acid in an organic water imasoaera miscible organic solvent with an aqueous solution of an alkali metal bisulfite. 1

4. A process for decolorizing monomeric a-ethacrylic acid, the color of the a-ethacrylic acid being caused by the presence of colored oxidation products of phenolic polymerization inhibitors, comprising treating a solution of the colored a-ethacryllc acid in an organic water immiscible organic solvent with an aqueous solution of an alkali metal bisulfite.

5. A process for decolorizing monomeric a-methacrylic acid, the color of the u-methacrylic acid being caused by the presence of colored oxidation products of phenolic polymerization inhibitors, comprising treating a solution of the colored a-methacrylic acid in an organic water immiscible organic solvent with an aqueous solution of sodium bisulfite.

6. A process for decolorizing monomeric a-ethacrylic acid, the color of the. a-ethacrylic acid being caused by the presence of colored oxidation products of phenolic polymerization inhibitors, comprising treating a solution of the colored a-ethacryllc acid in an organic water immiscible organic solvent with an aqueous solution of sodium bisulfite.

I WILLIAM P. UTERMOHLEN, JR. 

